Improving Nutrient Removal While Reducing Carbon Footprint at Three Swiss WWTPs Thanks to Advanced Control

Aeration consumes about 60% of the total energy of a WWTP and therefore makes up for a major part of its carbon footprint. Introducing advanced process control can help plants to reduce their carbon footprint and at the same time improve effluent quality through making available unused capacity for denitrification, if the ammonia concentration is below a certain set-point.Measuring and control concepts are a cost-saving alternative to the extension of reactor volume. However, they also involve the risk of violation of the effluent limits due to measuring errors, unsuitable control concepts or inadequate implementation of the measuring and control system. Dynamic simulation is a suitable tool to analyze the plant and to design tailored measuring and control systems.During this work, extensive data collection, modeling and full-scale implementation of aeration control algorithms were carried out at three conventional activated sludge plants with fixed pre-denitrification and nitrification reactor zones. Full-scale energy savings in the range of 16-20 % could be achieved together with an increase of total nitrogen removal of 40%.